Method for producing a micromechanical component, and a component produced according to said method

ABSTRACT

The present invention relates to a method for manufacturing a micromechanical component ( 100 ), that has at least one hollow space ( 110 ) and a functional element ( 12 ) that is provided at least partially in the hollow space ( 110 ) and/or a functional layer ( 13   a   , 13   b   , 13   c ) that is provided at least partially therein, and to a micromechanical component ( 100 ) that is manufactured in accordance with the method, according to the species of the relevant independent patent claim.  
     To reduce manufacturing costs, the functional element ( 12 ) and/or the functional layer ( 13   a   , 13   b   , 13   c ) is provided with a first protective layer ( 41; 71 ) at least in an area that directly or indirectly borders on a first sacrificial layer ( 52 ), which temporarily occupies the space of the hollow space ( 22 ) that is subsequently formed in one or a plurality of etching steps (FIG.  4 ; FIG.  7 ), the material of the first protective layer ( 41 ) being selected such that at least one etching process and/or etching medium, which etches or dissolves the first sacrificial layer ( 52 ), either does not substantially attack the first protective layer ( 41; 71 ) or does so only at a reduced etching rate in comparison to the first sacrificial layer ( 52 ).

BACKGROUND INFORMATION

[0001] The present invention relates to a method for manufacturing amicromechanical component and to a micromechanical component that ismanufactured in accordance with the method, according to the species ofthe relevant independent patent claim. German Patent 195 37 814 A1describes the design of a sensor-layer system and a method for thehermetic encapsulation of sensors in surface micromechanics.

ADVANTAGES OF THE INVENTION

[0002] In contrast, the method according to the present invention havingthe characterizing features of the relevant independent patent claimhas, in particular, the advantage that a hermetically sealed, closed-offcomponent can be manufactured in a more cost-effective manner. As aresult of the measures indicated in the dependent patent claims,advantageous refinements and improvements of the method and of thecomponent are made possible in accordance with the relevant independentpatent claims.

[0003] In contrast to the familiar components, a component according tothe present invention is characterized by a significant reduction in thesurface required for the encapsulation, which leads to significant costreduction as a result of the reduction in the surface area. In acomponent according to the present invention, such as a sensor, thefreedom of motion for movable structures called for in the component ispreserved, and this is so even if lateral amplitudes of more thanapproximately 2 μm must be achieved for the structures. This can be thecase, for example, if the movable structure, i.e., the functionalelement, is a rotational oscillator. On the other hand, the maximumdeflection of the movable structures, e.g., in a sensor, perpendicularto the latter can be limited to amplitudes between roughly 2 and 20 μm,which significantly increases, in particular, the falling sturdiness ofa component according to the present invention, in contrast to the knowncomponents. The movable structure, e.g., a sensor structure, in thecomponent according to the present invention is surrounded by a hollowspace in a gas- and/or water-tight manner, so that a defined, lastinglystable damping of the motion of the movable structure, e.g., the sensorstructure, can be brought about in the hollow space, for example,through the gas pressure of a gas enclosed in the hollow space. Theencapsulation according to the present invention is characterized bygreat mechanical stability, so that a component according to the presentinvention can stand up without difficulty to a hydrostatic pressure suchas occurs, for example, in the so-called mold pressure during theprocess of packing micromechanical components in a plastic housing.Finally, a component according to the present invention, e.g., a sensoraccording to the present invention, is characterized by a lowtopography, as a result of which it becomes possible, for example, touse so-called flip-chip technology in assembling the component.

[0004] The method according to the present invention preferably doeswithout the familiar use of oxide layers that have a thickness of morethan roughly 2 μm. Rather, thick layers are used that are advantageouslyconfigured largely in polycrystalline silicon, thus significantlyreducing the mechanical stresses arising from differing thermalcoefficients of expansion. This leads to a significantly improvedplanarity in the substrate. The method according to the presentinvention makes possible the problem-free use of optical lithographysteps, since topographies of more than 6 μm are preferably avoided.Finally, one or a plurality of isotropic etching processes is used forremoving one or a plurality of sacrificial layers (filler material) inthe micromechanical component, e.g., creating a hollow space which has amovable structure. Isotropic (silicon) etching processes of this typeare, e.g., those in which the etching media XeF₂, ClF₃, ClF₅, orplasma-activated NF₃, Ar/F₂, or SF₆ are used. In contrast to thefamiliar methods, in this context, the removal is carried out withoutthe risk of the structure to be exposed adhering at the higher ablationrate of the filler material to be removed.

DRAWINGS

[0005] The present invention is discussed in greater detail below on thebasis of drawings that are not necessarily full scale, identicalreference numerals designating the same or equivalent layers or parts.The following are the contents:

[0006]FIG. 1 depicts a cross-section of an acceleration sensor in thearea of its functional element, i.e., sensor element;

[0007]FIG. 2 depicts a cross-section of the area depicted in FIG. 1along the sectional line A-B in FIG. 1, in which a contact terminal hasalso been included; and

[0008] FIGS. 3-12 depict a method according to the present invention formanufacturing the acceleration sensor according to the present inventiondepicted in FIGS. 1 and 2.

[0009] On a substrate 10 that is depicted in FIG. 2, a sensor element 12of an acceleration sensor 100 is structured. This sensor element is madeup of a movable central mass, i.e., seismic mass 11 a, arranged onspring body 16 (of which, for reasons of simplicity, in FIG. 1 only onesingle spring body 16 is depicted), the central mass having movableelectrode fingers, or electrodes 11, that are provided in perpendicularfashion on the latter. Central mass, or seismic mass 11 a, is linked tosubstrate 10 via spring bodies 16 and via anchoring structures 17 (ofwhich, for reasons of simplicity, in FIG. 1 also only a single one isdepicted), so that central mass 11 a can be deflected by an accelerationacting upon it in a direction that is essentially perpendicular toelectrode fingers 11. As a result, the position of central mass 11 a ischanged with respect to the fixed electrode fingers, i.e.,counter-electrodes 12 a and 12 b. This change in position is evaluated,in a familiar manner, via electrical terminals on counter-electrodes 12a and 12 b as well as via printed circuit traces 14 a and 14 b leadingto the outside. In each case, three electrodes 12 a, 11, 12 b arearranged in a so-called interdigital arrangement, this arrangement ineach case forming a capacitor element, which is provided between twolaterally adjoining separating or support structures 13 a. Thedeflection of movable electrode fingers 11 is limited by stop arms 18(of which, for reasons of simplicity, in FIG. 1 only a single one isdepicted) and by stop knobs 19 a (for x-deflections) and 19 b (fory-deflections). Stop knobs 19 c and 19 d are advantageously provided inthe area of spring bodies 16, preventing spring bodies 16 from adhering.

[0010] It is obvious that it is possible in accordance with the presentinvention to provide two or more capacitor elements between twoadjoining support structures 13 a. Furthermore, alternatively oradditionally, support structures can be provided which penetrate throughcutouts in central mass 11 a and which are connected to substrate 10(not depicted).

[0011] Support structure 13 a is preferably made entirely of silicon,thus effectively avoiding an underetching of support structure 13 a inresponse to the etching of the sacrificial layers, i.e., etching, orremoving, a lower sacrificial layer 31 and an upper sacrificial layer 52(see FIGS. 10 and 11), as is required in the method according to thepresent invention for manufacturing a component according to the presentinvention as described below on the basis of FIGS. 3 through 12. Printedcircuit traces 14 a and 14 b run through support structures 13 c insupport structure 13 a, sacrificial layers insulating the printedcircuit traces from the support structures. A support structure 13 bfacing contact terminal 15 of acceleration sensor 100, for the externalcontacting of printed circuit traces 14 a and 14 b, i.e.,counter-electrodes 12 a and 12 b, also has an electrically insulatedpassage for circuit traces 14 a and 14 b.

[0012] Using the process sequence described below in detail on the basisof FIGS. 3 through 12, a supporting cap layer, inter alia, is createdover acceleration sensor 100, depicted in FIG. 1 in a partial cutawayview. Cap layer 20 is supported on support structures 13 a viaconnectors 23 such that hollow spaces 22 extend over the capacitorelements. Hollow spaces 22 have a width, which preferably lies in arange between roughly 20 μm and 200 μm. Cap layer 20 is provided with aperforation 21, which for reasons of simplicity is only designated usingtwo reference numerals 21, so as to be able to etch, i.e., remove,sacrificial layers 31 and 52 selectively with respect to the componentstructure, the sacrificial layers being used in the manufacturingprocess of acceleration sensor 100. After the etching of the sacrificiallayers, perforation 21 of component, i.e., acceleration sensor 100, ishermetically sealed up by a sealing layer 24. For acceleration sensorsor gyrometers, a vacuum or a gas having a defined pressure can beenclosed in hollow space 22 for generating a defined damping of themovement of the functional element, such as movable electrode fingers11. In addition, it is also conceivable to use an insulating fluidhaving a suitable viscosity, such as an oil-like fluid, in the case ofother components, such as actuators.

[0013]FIG. 3 depicts the basic design of the sensor structure ofacceleration sensor 100 by way of example for the part of theacceleration sensor depicted in FIG. 2 as A, as it is seen after a deepstructuring and before the etching of the sacrificial layers. Onsubstrate 10, a sacrificial layer 31 is deposited, which can be made upof, for example, one or plurality of SiO₂ layers. Deposited then onsacrificial layer 31 is the sensor element, i.e., functional element 12,which can be made of epipoly silicon, i.e., epitaxially producedpolycrystalline silicon, which was deposited on a thin poly-Sinucleation layer 12′ (start poly). In a Si-deep-structuring method(trench etching), sensor element 12 of acceleration sensor 100 isproduced, such as, for example, fixed electrode fingers 12 a and 12 band electrode fingers 11 arranged in perpendicular fashion on movablecentral mass 11 a. Before the etching of the sacrificial layers, thesefunctional elements are fixedly anchored on sacrificial layer 31. As aresult of a pre-structuring of sacrificial layer 31, it is possibleduring the deposition and structuring of plane 12, to also producefixing points on substrate 10, support structures 13 a.

[0014] As is depicted in FIG. 4, a roughly 10 nm to 1 μm thin firstprotective layer 41 is deposited on entire sensor element 12 using a CVDprocess. The result, in areas 41 a and 41 b of first protective layer41, is a complete covering of sensor element 12 on the so-calledelectromechanically functional level. In areas 41 c of protective layer41, lower sacrificial layer 31 is covered. According to the presentinvention, attention should be paid that protective layer 41, in ahermetically sealing manner, cover sensor element 12 on theelectromechanically functional level, such as, in particular, movableelectrode fingers 11 and counter-electrodes 12 a and 12 b, as well asother components of acceleration sensor 100, such as support structures13 a, which are not made of the same material as protective layer 41.Protective layer 41 is preferably made of SiO₂. Furthermore, lowersacrificial layer 31 can be made of, for example, SiO₂, as in thisexemplary embodiment. Sacrificial layer 31, in one alternativeembodiment, can be enclosed in further protective layers (not depicted),and it is then preferably made of polycrystalline silicon.

[0015] Preferred deposition processes for generating protective layer 41are CVD processes, such as PECVD (plasma-enhanced CVD) or LPCVD(low-pressure CVD), it being important to achieve the best possiblecoverage of the lateral surfaces of the components of sensor element 12on the electromechanically functional level, areas 41 b.

[0016] As depicted in FIG. 5, in a further process step, a thinstart-poly-Si layer 51, i.e., a polycrystalline silicon layer having thefunction of a seed or nucleation layer, is deposited on protective layer41. Due to the large aspect ratio, i.e., the ratio of the height to thewidth of gaps in area 51 c of sensor element 12, it can happen thatstart-poly-Si layer 51 is mainly deposited in upper areas 51 a on sensorelement 12, and the deposition on lateral walls 51 b of sensor element12 only takes place in their upper area. Areas 51 c at the foot ofsensor element 12, above areas 41 c of protective layer 41, are coatedwith start-poly-Si layer 51 only in the case of the larger gap widthsbetween electrodes, i.e., support structures of sensor element 12.Deposited on start-poly-Si layer 51, using an epitaxy process, or LPCVDprocess, is a polycrystalline silicon layer, a so-calledfiller-epipoly-Si layer, sacrificial layer 52, start-poly-Si layer 51merging into upper sacrificial layer 52. “Epi” signifies “epitaxial” and“poly” stands for “polycrystalline.” Upper sacrificial layer 52 in thedeposition may already be doped using phosphorus; nevertheless, it ispreferably deposited undoped. The layer thickness of upper sacrificiallayer 52 is selected such that sensor element 12 is completely coveredby it. This is typically the case in a layer thickness of roughly 5 to30 μm.

[0017] A filler-epipoly-Si layer, i.e., sacrificial layer, having such athickness usually has a pronounced roughness. In addition, thetopography of sensor element 12 comes through in upper sacrificial layer52. Therefore, the topography of sensor element 12 and the roughness ofupper sacrificial layer 52 are planarized in a further process step.This takes place using a chemical-mechanical polishing process (CMP), inwhich upper sacrificial layer 52 is thinned down to a level 53. Level 53lies above sensor element 12. Height h over sensor element 12 is roughlybetween 1 and 30 μm; the preferred height is roughly 4 to 6 μm.

[0018] After the planarization, the structuring of upper sacrificiallayer 52 is carried out using a familiar Si-etching process, asillustrated in FIG. 6. In this context, upper sacrificial layer 52 isleft alone in areas, in which are arranged the movable sensor elements,such as spring bodies 16, movable electrode fingers 11, fixed electrodefingers, i.e., counter-electrodes 12 a and 12 b, and central mass, i.e.,seismic mass 11 a. Upper sacrificial layer 52 is removed over separatingor support structures 13 a down to silicon-oxide protective layer 41.

[0019] According to FIG. 7, a second protective layer 71 is applied tostructured upper sacrificial layer 52. This protective layer 71 ispreferably made of the same material as first protective layer 41,specifically SiO₂. Protective layer 71 is removed over supportstructures 13 a in area 72 using a familiar process. According to thepresent invention, it must be assured that upper sacrificial layer 52 onentire acceleration sensor 100 is hermetically surrounded by protectivelayers 41 and 71, and that there is no connection between sensor element12 and upper sacrificial layer 52. Sensor element 12 and uppersacrificial layer 52 are preferably made of the same material.Furthermore, it is preferable that protective layers 41 and 71, on thestationary areas, i.e., support structures 13 a, merge into each other,or contact each other sealingly.

[0020] As depicted in FIG. 8, a further start-poly-Si layer, ornucleation, or germ layer 81, is applied over the entire surface onprotective layer 71 and on exposed areas 72 at a preferred layerthickness of between roughly 300 nm and 2 μm. Deposited on thisstart-poly-Si layer 81 is a further poly-silicon layer 82 using anepitaxial process or LPCVD process. The layer thickness isadvantageously between roughly 2 and 50 μm. Poly-silicon layer 82 issubsequently thinned and planarized down to a level 83. Residualthickness k between second protective layer 71 and level 83 shouldpreferably be between roughly 2 and 50 μm. Poly-silicon layer 82 can bedoped during the deposition or in a subsequent process step.

[0021] One significant aspect of the present invention is therefore tocompletely coat, in an advantageously thin protective layer, e.g., ofsilicon oxide, a structured poly-Si-functional layer, e.g., a movablesensor element or another functional element, for producing a hollowspace that, in a micromechanical component, at least partially surroundsthe functional layer, i.e., the functional element (see FIG. 4), and todeposit on this thin protective layer a further polycrystalline siliconlayer, i.e., filler layer, an upper sacrificial layer (see FIG. 5). As aresult of the polycrystalline silicon layer, the structured level, i.e.,the functional layer of the component, is embedded and completelycovered.

[0022] A further important aspect of the present invention is toplanarize the upper sacrificial layer and to close it off to the outsideusing a further, thin protective layer (see FIGS. 6 and 7). Deposited onthis protective layer, closing off the upper protective layer to theoutside, is a thick poly-silicon layer, which as a supporting layerforms a component or sensor cap (See FIG. 8).

[0023] According to the present invention, it is provided that the uppersacrificial layer is made of the same material as the functional layer.The sacrificial layer used in accordance with the present invention isenclosed by two sealed protective layers, so that the sacrificial layercan be selectively etched down to the protective layers, or can beremoved through etching. The protective layers are then removed byetching the lower sacrificial layer. In this regard, it is advantageousthat, as a result of the use, according to the present invention, of afiller layer, i.e., upper sacrificial layer, large gap widths in thefunctional layer, e.g., a layer that represents the sensors, can befilled in (see FIG. 5). As a result, it is possible to achieve a highdegree of freedom in the design of the component, or in the design ofthe sensor, especially with regard to the freedom of motion of theoscillator structures, or movable structures, in the component, orsensor.

[0024] As a result of a planarization step on the upper sacrificiallayer (see FIG. 8), topographies are evened out, thus making possible afurther structuring of the upper sacrificial layer usingphotolithography. A planarization of this type is only made possible bythe use according to the present invention of silicon as a filler layermaterial, i.e., sacrificial layer. In the method according to thepresent invention, an isotropic silicon-etching step is preferablyemployed, which permits a removal of the upper sacrificial layer, i.e.,filler layer, that is rapid and free of residue.

[0025] A further advantage of the method according to the presentinvention is that metal contacts for the external contacting of thefunctional layer, i.e., the sensor elements, and for the furthertransmission of the measuring signals emitted by the sensor elements forevaluation can only be applied at the end of the process.

[0026] The method according to the present invention can be used forproducing a multiplicity of sensor and actuator components in surfacemicromechanics. It is also possible, on one single chip sensor oractuator, to integrate structures along with an evaluation circuit forevaluating the measuring signals emitted by these structures.

[0027] After the planarization and doping of poly-silicon layer 82, thelatter is provided with a lacquer or oxide mask 83 and is structuredusing a known silicon deep-etching process (see FIG. 9). In thiscontext, perforation holes 84 are created through poly-silicon layer 82to upper sacrificial layer 52, the holes, in the deep structuring ofsacrificial layer 82, ending only at second protective layer 71. Thearea of support structures 13 a is left open in the perforation for thefixed binding of cap layer 20, i.e., sealing layer 24. In the deepstructuring, a sufficiently thick lateral wall passivation 85 isdeposited, it being preferably a fluoride-containing polymer compound.Lateral wall passivation 85 is a layer which assures that poly-siliconlayer 82 is not attacked during a subsequent silicon etching step. Inaddition to polymers, for the lateral wall passivation, it is alsopossible, for the lateral wall protection, in addition to protectivelayers 41 and 71, to deposit a further thin protective layer, forexample, of silicon oxide.

[0028] As indicated in FIG. 10, protective layer 71 in a subsequent stepis removed in perforation holes, i.e., trenches 84, using a familiaretching process. As a result, direct access to upper sacrificial layer52 is generated for its subsequent etching.

[0029]FIG. 11 depicts a central step for creating cap layer 20, in whichupper sacrificial layer 52 has been selectively etched with respect toprotective layers 41 and 71. For this purpose, isotropic etchingprocesses are preferably used, e.g., those in which are used etchingmedia XeF₂, ClF₃, ClF₅, or plasma-activated NF₃, Ar/F₂, or SF₆. In theselective etching of upper sacrificial layer 52, with respect toprotective layers 41 and 71, the etching of upper sacrificial layer 52stops at the surfaces bordering on protective layers 41 and 71. Anetching of the lateral walls of perforation holes 84, withinpoly-silicon layer 82 forming cap layer 20, is suppressed by lateralwall passivation 85 that is applied. At the end of the process, uppersacrificial layer 52 is entirely etched, or dissolved. A hollow space 22is created over sensor element 12, which is covered over by a stable,supporting poly-silicon layer 82, or cap layer 20 (see, especially FIG.2). In accordance with FIG. 12, after the etching of upper sacrificiallayer 52, protective layers 41 and 71, which represent auxiliary layers,and lower sacrificial layer 31 are selectively etched with regard tosensor element 12 and poly-silicon layer 82, which forms cap layer 20(see FIG. 2). For this purpose, a method based on the use of a vaporousHF/H₂O mixture can be used for etching SiO₂ layers. In this method,gaseous HF and H₂O penetrates through perforation holes 84 of cap layer20 and arrives at protective layers 41 and 71, and after they areetched, at lower sacrificial layer 31. After this etching step,protective layers, i.e., oxide layers 41 and 71, and lower sacrificiallayer 31 are removed, and all the movable structures of sensor element12, such as central mass 11 a, spring bodies 16, stop arms 18, andmovable electrode fingers 11, are detached from substrate 10 (seeespecially FIGS. 1 and 2). Subsequent to this etching step, in a gaseousatmosphere, perforation holes 84 of poly-silicon layer 82, i.e., of caplayer 20, are covered by a covering layer 120. Covering layer 120 ispreferably between roughly 1 and 20 μm thick and is made of, forexample, an insulator, advantageously SiO₂, which preferably has beendeposited using a PECVD process. In the deposition of covering layer120, a process gas is preferably enclosed in hollow space 22 at the sametime, thus making it possible to set the dynamic damping of the movablecomponents of sensor element 12 of acceleration sensor 100 according tothe present invention as a function of the pressure of the enclosedprocess gas and/or of its type. Enclosing a gas that dampens the motionof the movable components provided in acceleration sensor 100 accordingto the present invention can also of course take place in a furtherprocess step that is independent of the deposition process.

[0030] After the deposition of covering layer 120, metallic printedcircuit traces 14 a and 14 b, as well as contact terminal 15, aremanufactured in a familiar manner.

[0031] In one alternative embodiment of the present invention (notdepicted), it is provided that lower sacrificial layer 31 and uppersacrificial layer 52 are, in each case, made of polysilicon, whereaslower sacrificial layer 31 in the method depicted in FIGS. 3 through 12is made of SiO₂. Deposited on substrate 10 in the alternative embodimentis a lower protective layer (undepicted). Subsequent thereto is thedeposition of the polysilicon sacrificial layer, on which subsequentlyan upper protective layer (undepicted) is deposited, so that lowersacrificial layer 31 is completely enclosed by the lower and the upperprotective layer. The lower protective layer functions to protectagainst etching corrosion of substrate 10, and the upper protectivelayer protects sensor element 12, i.e., functional layers 13 a, 13 b, 13c, against etching corrosion in response to the selective etching, i.e.removal, of the lower sacrificial layer. The protective layers for bothsacrificial layers are preferably made of silicon oxide, so that the twosacrificial layers of the same material can be removed in one single ora plurality of etching steps.

[0032] Due to the planarity of the component that can be manufacturedusing the method according to the present invention, such as theacceleration sensor depicted in the Figures, it is easily possible tointegrate sensor/actuator structures and integrated evaluation circuitson one single chip, or component (undepicted). For this purpose, thelevel of the sensor element that has an upper sacrificial layer and acap layer must be produced in the manner described. To avoid impairingelectronic circuits in a chip or component of this type, it isadvantageous to carry out the perforation of the cap layer, the etchingof the upper sacrificial layer, the removal of the protective layers,and the enclosing of the hollow space by a covering layer, as well asthe electrical connection of the contact terminals, after themanufacture of the circuits of a chip, or component, of this type. Inthese process steps, even lower temperatures are created, so that thecircuits, which can, for example, have transistors, are not damaged.

[0033] The preceding explanations of the present invention make clearthat the present invention is not limited to an acceleration sensoraccording to the present invention, or to a method according to thepresent invention for manufacturing it, but rather makes possible themanufacture of a multiplicity of micromechanical components, which havea hollow space, in particular, a hermetically sealed hollow space. Thisis especially the case if, in the hollow space, movable elements areprovided from the entire range of micromechanics, such as sensorelements or also components of a micropump, etc.

1. A method for manufacturing a micromechanical component (100), whichhas at least one hollow space (22) and one functional element (12) thatis provided at least partially in the hollow space (22) and/or onefunctional layer (13 a, 13 b, 13 c) that is provided at least partiallytherein, the functional element (12) and/or the functional layer (13 a,13 b, 13 c) being provided with a first protective layer (41; 71) atleast in an area that directly or indirectly borders on a firstsacrificial layer (52), which temporarily occupies at least partiallythe space of the hollow space (22) that is subsequently formed in one ora plurality of etching steps (FIG. 4; FIG. 7), the material of the firstprotective layer (41; 71) being selected such that at least one etchingprocess and/or etching medium, which etches or dissolves the firstsacrificial layer (52), either does not substantially attack the firstprotective layer (41; 71) or does so only at a reduced etching rate incomparison to the first sacrificial layer (52), on the side of thesecond protective layer (71) facing away from the first sacrificiallayer (52), a cap layer (20; 82) being provided that at least partiallysurrounds the hollow space (22), and for the functional element (12)and/or for the functional layer (13 a, 13 b, 13 c) and for the firstsacrificial layer (52) and/or for the second sacrificial layer (31), atleast partially the same material being selected, such as, specifically,silicon, which is preferably polycrystalline.
 2. The method as recitedin claim 1, wherein, on at least one side of the first sacrificial layer(52) facing away from the functional element (12) and/or the functionallayer (13 a, 13 b, 13 c), a second protective layer (71) is provided onthe first sacrificial layer (52) (FIG. 7), the material of the secondprotective layer (71) being selected such that at least one etchingprocess and/or etching medium, which etches or dissolves the firstsacrificial layer (52), either does not substantially attack the secondprotective layer (71) or does so only at a reduced etching rate incomparison to the first sacrificial layer (52).
 3. The method as recitedin one of claims 1 through 2, wherein the functional element (12) and/orthe functional layer (13 a, 13 b, 13 c) borders directly or indirectlyon a second sacrificial layer (31), and the second sacrificial layer(31) is selected such that at least one etching process and/or etchingmedium, which etches or dissolves the second sacrificial layer (31),either does not substantially attack the functional element (12) and/orthe functional layer (13 a, 13 b, 13 c) or does so only at a reducedetching rate in comparison to the second sacrificial layer (31), siliconbeing preferably selected for the functional element (12) and/or thefunctional layer (13 a, 13 b, 13 c) at least on the side facing thesecond sacrificial layer (31), and silicon oxide being selected for thesecond sacrificial layer (31).
 4. The method as recited in one of claims1 through 3, wherein, between the functional element (12) and/or thefunctional layer (13 a, 13 b, 13 c) and the second sacrificial layer(31), a third protective layer is provided, which is selected such thatat least one etching process and/or etching medium, which etches ordissolves the second sacrificial layer (31), either does notsubstantially attack the third protective layer or does so only at areduced etching rate in comparison to the second sacrificial layer (31),the second sacrificial layer (31) preferably being made of the samematerial as the first sacrificial layer (52), such as, specifically,silicon, and/or the third protective layer is made of the same materialas the first and/or second protective layer (41, 71), such as,specifically, silicon oxide.
 5. The method as recited in one of thepreceding claims, wherein the first protective layer (41) and the secondprotective layer (71) all but completely enclose the first sacrificiallayer (52), and/or the third protective layer and a fourth protectivelayer all but completely enclose the second sacrificial layer (31). 6.The method as recited in one of claims 1 through 5, wherein, for thefirst protective layer (41) and/or for the second protective layer (71)and/or for the third protective layer and/or for the fourth protectivelayer, at least partially the same material is selected, such as,specifically, an oxide, such as silicon oxide.
 7. The method as recitedin one of claims 1 through 6, wherein the first sacrificial layer (52)and/or the second sacrificial layer (31) is removed in one or aplurality of isotropic etching steps, such as, specifically, siliconetching steps.
 8. A micromechanical component (100) which has at leastone hollow space (22) and one functional element (12) that is providedat least partially in the hollow space (22) and/or one functional layer(13 a, 13 b, 13 c) that is provided at least partially therein, whereinthe component is manufactured in accordance with a method recited in thepreceding claims.
 9. The micromechanical component as recited in claim8, wherein the component (100) is a sensor and/or an actuator componentand/or the functional element (12) and/or the functional layer (13 a, 13b, 13 c) has at least one gap (51 c) having a width that is large inrelation to the thickness of the functional element (12) and/or thefunctional layer (13 a, 13 b, 13 c), i.e., a large so-called aspectratio.